In general, an image sensor or a display panel has its intrinsic gamma properties that need to be considered in a display system including the image sensor or the display panel, and described with reference to FIGS. 1, 2A, 2B, 2C and 2D.
FIG. 1 is a block diagram illustrating a display system including a liquid crystal display (LCD) panel 150.
The display system illustrated in FIG. 1 includes a controller 110, a source driver 120, a gradation voltage generator 130, a gate driver 140 and the LCD panel 150. In FIG. 1, the source driver 120 includes a decoder DEC and a buffer BUF. Although not illustrated in FIG. 1, the gradation voltage generator 130 may be included inside the source driver 120.
The decoder DEC receives input of a plurality of gradation voltages V<0> to V<255> generated in the gradation voltage generator 130. The decoder DEC further outputs, from among the gradation voltages V<0> to V<255>, a gradation voltage corresponding to display data DATA as a display data voltage V_data that is then applied to the LCD panel 150 through the buffer BUF. The brightness of the LCD panel 150 (referred to as B_panel) corresponds to the display data voltage V_data.
FIGS. 2A and 2D are graphs each illustrating an interrelationship between the display data DATA and the display data voltage V_data, and FIGS. 2B and 2C are graphs each illustrating an interrelationship between the display data voltage V_data and the brightness of the LCD panel B_panel. In FIGS. 2A through 2D, <0> to <255> each indicate gradation.
For example, it will be considered that a gamma curve of the LCD panel 150 illustrated FIG. 1 is like the one of FIG. 2B. As illustrated in FIG. 2A, when display data voltages V_data<0> to V_data<255> having the same voltage distance (ΔV1=ΔV2) are generated in response to display data DATA <0> to DATA <255> of the gradation, and the display data voltages V_data<0> to V_data<255> having the same voltage distance ΔV1=ΔV2 are applied to the LCD panel 150, it is difficult to expect a linear brightness output, as illustrated in FIG. 2B.
For the linear brightness output illustrated in FIG. 2C, the voltage distance ΔV of the display data voltages V_data<0> to V_data<255> needs to be adjusted by the gradation voltage generator 130. That is, the gradation voltage generator 130 adjusts a voltage level of each of the gradation voltages V<0> to V<255>, so that the interrelationship between the display data DATA and the display data voltage V_data is like that of FIG. 2D. Accordingly, the display system is realized with proper gamma properties by adjusting each voltage level of each of the gradation voltages V<0> to V<255>. Also, not all display panels pursue the linear brightness output. In some case, the voltage levels of the gradation voltages V<0> to V<255> may be adjusted to delicately display the gradation of a specific portion.
To prevent the deterioration of a liquid crystal in the driving of the LCD panel 150, an inversion driving method is used during which the display data voltage V_data is applied so that an alignment direction of the liquid crystal changes per predetermined period. The inversion driving method can be classified as one of a frame inversion type, a line inversion type, a column inversion type, and a dot inversion type, depending on the set up of a pixel group that is being simultaneously inverted. Furthermore, the inversion driving method can be classified as a Y-axial symmetric type and an X-axis symmetric type, depending on whether the display data DATA or the gradation voltages V<0> to V<255> are being inverted.
The gradation voltage generator 130 included in the display system needs to generate the gradation voltages <0> to V<255> while considering the aforementioned gamma properties and inversion driving.